The use of automatic tuning circuits to enhance the response of a multi-channel RF transmitter circuit has been widely described in the prior art. In general, however, such systems are directed to automatic tuning systems which electromechanically vary capacitance and inductance in response to detected phase differences.
Additionally, automatic switching has been utilized to match the output impedence of transmitter circuits to that of a particular antenna. Again, these are generally directed to electromechanically varying the capacitance or inductance or by electromechanically inserting fixed parameter capacitors and inductors to form a specific LC network circuit between the output of a power amplifier and an antenna transmit/receive switch.
In those instances where attention has been directed to tuning the power amplifier for band-pass filtering, the tunable filter has, in general, been designed around a three gang variable inductor and a band select switch which is incorporated as part of the accompaning transmitter. The tuning of these components is controlled by mechanical linkages which permitted sufficient filtering to enable the equipment to be set up for re-transmission and co-located operation.
More recently the prior art has been directed to the use of solid state devices with their operational speed advantage. Unfortunately, due to the low Q inherent in solid state devices the problems of selectivity has limited the use of such devices in multi-megacycle bandwidth applications.
Accordingly, there is a need for a solid state automatically tunable power amplifier which will provide very selective filtering across a multi Megahertz range to reduce broad band noise to a level that will permit re-transmission and co-located operation of the transceiver. Additionally, to enhance equalization of the output signal across the spectrum covered by the multiple channels of the transmitter, a requirement exists for an automatic level control which controls the output of the power amplifier to a preset level and reduces the output power there if in relation to an increase in the voltage standing wave ratio (VSWR) load of the system.